Safety device for electric machines



Aug. 24, 1937. o. SCIAKY 2,091,219

SAFETY DEVICE FOR ELECTRIC MACHINES Filed Feb. 10, 19:54 2 Shedts-Sheet 1 Mic/m:

iaefssae 6 6 Mew/06mm E l lfezssues 65065 A 24, 1937- D. SCIAKY 2,091,219

SAFETY DEVICE FOR ELECTRIC MACHINES Filed Feb. 10, 1934 2 Sheets-Sheet 2 Fig.5

Patented Aug. 24, 1937 UNITED STATES PATENT OFFICE Application February 10, 1934, Serial No. 710,760

7 In France February 14, 1933 2 Claims.

The present invention relates to electric welding machines and especially to electric welding machines the good working oi which is dependent on the circulation of a cooling fluid.

ii It is known for instance that the cables of the secondary circuit or movable electric welding machines are necessarily of a relatively small cross section, which makes it absolutely necessary to cool them by means of a circulation of water. When, due to a mistake, the current is switched on without the water of the system being caused to circulate, there is a serious risk of overheating the conductors and oiinjuring their insulating coating.

The object of the present invention is to pro vide a safety device for obviating these drawbacks.

The device according to my invention is characterized in that itstops the working of the machine or prevents it from being brought into action when the circulation of the cooling fluid is not established, when this circulation of fluid is stopped for any reason whatever, or when it becomes insufllcient.

Another objectis to provide the safetydevice according to my invention with warning means so that the operator may be aware that the machine is no longer working and of the reason of this stopping.

A preferred embodiment of the present invention will be hereinafter described with reference to the accompanying drawings, given merely by way of example, and in which:

Fig. 1 shows the electric connections of the device according to the present invention; and

Fig. 2 shows a detail.

Fig. 3 shows a modification.

In the example shown in the drawings, the working of the welding machine is controlled by a pressure-gauge i placed close to the outlet of the water circulation system through which the cables A connecting transformer B with the electrodes (Fig. 2) are cooled. It would not be so advantageous to branch the manometer to the circulation system close to the water inlet,

because, in this case, an obstruction of the conduits for the circulation of water would not cause the pressure to drop in the manometer. On the contrary, this pressure would rather tend 5 to increase and the rubber tube C that surrounds the conductors might even burst under the pressure of water beginning to vaporize. Consequently, the arrangement of the pressure gauge close to the water outlet constitutes a protection for the operator.

The pressure gauge i is provided with a contact i arranged to be closed for a minimum value of the pressure. This contact is inserted in a shunt including the coil 2 of a relay. This relay includes a contact 3 which is closed when coil 2 is not energized and another contact 4 which is closed only when this coil is energized. Contact 4 is inserted in a shunt arranged to feed current to a warning device, such as a lamp 5, an electric bell, or both. As for contact 3, it is inserted in a shunt which includes the coil 6 of the main contactor or switch and a circuit breaker I for controlling the working of the welding machine.

This main contactor or switch closes the circuit of the machine 8 when its coil is energized.

As soon as the pressure of the water drops at the outlet of the machine below the minimum value corresponding to the adjustment of the device, the circuit of relay 2 is closed by the contact I of the pressure-gauge l. The circuit of the coil 8 of the main switch is therefore opened at 3, so that the operator can no longer send electric current into the welding machine by acting on the control switch I. Simultaneously,

contact 4 is closed so that lamp 5 is switched on,

thus warning the operator that the welding machine is no longer working. Furthermore, lamp 5 may be, for instance, so arranged as to illuminate a panel on which is written Open the water circulation system.

In a welding machine having a pneumatic control of the electrodes including an electro-valve, I may insert the supplementary relay 234 in the circuit of the electro-valve, instead of inserting it in the circuit of the main contactor or switch. In this case, if the water circulation system comes to fail, it becomes impossible to establish the compressed air pressure.

I may also prevent the current from passing through the machine if the flow is controlled by a "pilot relay arranged to permit the closing of the welding circuit only when the electrodes exert the required pressure on the piece to be welded, as described in my French patent, filed January 23, 1933, for Improvements in electric welding machines.

Such an arrangement is shown by Fig. 3. In this figure, the movable electrode it moves with respect to the stationary electrode 20 under the action of a fluid under pressure acting, in cylinder 30, on a piston 40 operatively connected to the electrode l0 through a system of jointed links.

The fluid under pressure, for instance com pressed air, is fed from a pipe 66 and is conveyed to a three-way valve 9d, operated through an electro-magnetic relay ill. The outlets Hi and lid of this valve are connected through pipes 520 and are respectively to the opposite ends of cylinder 39.

The cylinders MI] and I50 are provided with pistons I fill and H0 respectively, which move in connection with a movable member I80, pivoted at i9!) to the stationary part of the device, Cyl inders M9 and Hill are respectively connected, through pipes 200 and 2H], on the one hand to pipe 50 and on the other hand to the portion of cylinder 30 in which compressed air acts on piston $13 for displacing the electrode Ill in a downward direction. Movable member I80 controls the working of the make and break device 22023ll.

The operation of this machine, which is connected with the safety device above described (by inserting make and break device 220-238 in the circuit of coil 6 and inserting contact 3 in a circuit branched to switch and including the 25 electro-valve 79, instead of connecting said contact 3 in series with coil 6 as in the preceding embodiments) is the following:

As long as the rate of flow of the cooling fluid is suiflciently high, contact 3 remains closed, and

the closing of switch 1 causes valve 70 to move distribution valve 90 in an upward direction. As soon as the electrode is applied against the piece of work with the desired pressure, the pressure acting on piston i5!) applies member I80 against contacts 220-430. This closes the circuit of coil 6 and the transformer feeds current to the electrodes.

If the rate of flow of the cooling fluid drops below a predetermined value, contact 3 opens,

as above explained. This does not immediately cut off the current flowing through the electrodes, but after the welding operation is completed, relay in can no longer operate and the working of the Welding machine is stopped as long as the rate of flow of the cooling fluid keep's below the predetermined value above referred to.

; This embodiment has the advantage that it does not stop a welding operation that is taking place, but nevertheless stops the working of the machine for further operations.

It should be well understood that the main feature of my invention is that the machine is prevented from working when the cooling becomes insufl'icient. My invention is not limited to the specific means described in the foregoing examples.

On the other hand, my invention is not limited to its application to welding machines but it can be utilized in connection with any other machines or plants in which the same problem is met with.

In a general manner, while I have, in the above aoeraie description, disclosed what I deem to be practical and efiicient embodiments of the present invention, it should be well understood that I do not wish to be limited thereto as there might be changes made in the arrangement, disposition and form of the parts without departing from the principle of the present invention as comprehended within the scope of the appended claims.

What I claim is:

1. In a machine including two electrodes and a welding transformer for feeding current to said electrodes, the combination of a primary circuit for said transformer, a make and break in said circuit, a relay for operating said make and break, a circuit for said relay, a fluid pressure responsive member for applying at least one of said electrodes against the piece of work, a source of fluid under pressure, means, including an electrically operated valve, and a circuit for said valve, for controlling the action of said fluid under pressure on said member, a make and break in the second mentioned circuit, means operative by the fluid pressure acting on said member, for bringing the last mentioned make and break to the closed position when said electrode is being applied against said piece of work with the desired pressure, secondary conductors for said transformer, a cooling fluid circulation system for said secondary conductors, means for preventing current from being sent through the third mentioned circuit, and means, responsive to the fluid pressure in said cooling fluid circulation system, for operating said last mentioned means,

2. In a machine including two electrodes and a welding transformer for feeding current to said electrodes, the combination of a primary circuit for said transformer, a make and break in said circuit, a relay for operating said make and break, a circuit for said relay, a fluid pressure operated memberfor applying at least one of said electrodes against the piece of work, a source of fluid under pressure for operating said member, means, including an electrically operated valve and a circuit for said valve, for controlling the operation of said member by said fluid, a make and break in the second mentioned circuit, means operative by the fluid pressure acting on said member for bringing the last mentioned make and break to the closed position when said electrode is being applied by said member against the piece of work with the desired pressure, secondary conductors for said transformer, a cooling fluid circulation system for said conductors, and means, responsive to variations of the rate of flow of said cooling fluid in said circulation system, for acting on said third mentioned circuit so as to prevent further operation thereof once it has been stopped working in the case of said rate of flow dropping below a predetermined minimum value.

DAVID SCIAKY. 

